From the unpublished document DE 10 2011 080 069.7 by the present applicant, a range-change transmission device designed as an automated range-change transmission of a motor vehicle is known, which has a three-step main transmission of countershaft structure. In driving connection upstream from the main transmission is a two-step upstream transmission designed as a splitter group and downstream from the main transmission there is connected a two-step range group. An input shaft of the group transmission can be brought into functional connection with a drive aggregate of the motor vehicle and an output shaft of the group transmission can be brought into functional connection with an axle drive of the motor vehicle. An electric machine of the drive aggregate, which aggregate is formed as a hybrid drive, can be coupled to the splitter group by a planetary transmission gear system. The electric machine is connected to a first element of the planetary transmission. A second element of the planetary transmission is coupled to an input shaft of the splitter group and hence to the input shaft of the group transmission. A third element of the planetary transmission is connected to an output shaft of the splitter group and hence to an input shaft of the main transmission.
Furthermore, DE 10 2009 054 752 A1 describes a drive-train of a motor vehicle with a hybrid drive comprising an internal combustion engine and an electric machine, with an automated group transmission connected between the hybrid drive and an axle drive. The group transmission comprises at least one countershaft-designed three-step main transmission, in driving connection with the main transmission an upstream, two-step group in particular designed as a splitter group, and in driving connection downstream from the main transmission a two-stage group in particular designed as a range group. An input shaft of the group transmission can be connected by a controllable starting clutch to the internal combustion engine. An output shaft of the group transmission is connected to the axle drive. The electric machine of the hybrid drive is connected to the, or to each countershaft.
In both of these group transmissions in each case twelve gear ratios for forward driving can be engaged. Required gearshifts in the group transmissions are in each case carried out by engaging and disengaging gear steps in the area of the splitter group, the main transmission and/or the range group, by means of interlock-type shifting elements and in so-termed range shifts or group shifts. During range shifts, the required gearshift is in each case carried out only by disengaging a gear in the area of a group, i.e. only in the area of the splitter group, the main transmission or the range group, and engaging another gear in the same group. In contrast, gearshifts required during group shifts are carried out by engaging and disengaging gears in the area of at least two of the three groups of the group transmission.
Disadvantageously, gearshifts in automated group transmissions can only be carried out with traction force interruption, when the gearshift required can be carried out as a range shift in the area of the splitter group with corresponding assistance from the electric machine. This means that gearshifts are in each case only possible without traction force interruption between two adjacent gears. Thus, only six of the eleven possible gearshifts can be carried out without traction force interruption. All other gearshifts in the group transmissions, which are carried out by range shifts in the area of the main transmission and/or in the area of the range group or by means of group shifts, cannot be carried out without traction force interruption. This results from the fact that the respective interlocking shifting elements involved in the gearshift in the area of the main transmission and/or the range group cannot be opened or closed while under load, and cannot be actively changed without traction force interruption, either by means of the electric machine or by any other procedure, to an at least approximately load-free operating condition.
In contrast to gearshifts in the area of the splitter group, whose respective interlocking shifting elements to be actuated can be changed by means of the electric machine, without traction force interruption, to an at least approximately load-free operating condition as necessary for engagement or disengagement, the shifting elements of the main transmission and/or the range group to be actuated during the operation of the automated group transmission can only by changed to an operating condition necessary for their actuation, and thus at least approximately load free, by removing the load and thus by a complete traction force interruption. However, this results in an at least brief interruption of the traction force applied at the drive output. For well known reasons traction force interruptions are undesired, particularly in the case of utility vehicles such as trucks or the like, and especially when driving uphill and downhill.